In April 2009, Oracle announced that it had agreed to acquire Sun. Since Sun had acquired MySQL the previous year, this would mean that Oracle, the market leader for closed source databases, would get to own MySQL, the most popular open source database.
If Oracle acquired MySQL on that basis, it would have as much control over MySQL as money can possibly buy over an open source project. In fact, for most open source projects (such as Linux or Apache) there isn't any comparable way for a competitor to buy even one tenth as much influence. But MySQL's success has always depended on the company behind it that develops, sells and promotes it. That company (initially MySQL AB, then Sun) has always owned the important intellectual property rights (IPRs), most notably the trademark, copyright and (so far only for defensive purposes) patents. It has used the IPRs to produce income and has reinvested a large part of those revenues in development, getting not only bigger but also better with time.